I could take a villain who has no connections origin being changed for the sake of the story but if they make Ultron Iron Man centric it will truly be the first signs of me getting fed up with the MCU. I find it hard to believe a guy like Whedon who grew up on the classic Avengers story deviating that far from Avengers cannon. Pym creating and being responsible for Ultron is one of the Avengers cornerstone storylines and Pyms most defining element. Without that character point what would be the point of even having Hank and Jan exist. Ant-Man would have to focus on the lesser Ant-Men.